In a known manner, such a generator circuit breaker is opened to interrupt the electrical circuit that connects the generator to the transformer, and that is in general three-phase. The disconnector, which has no interrupting capability, is subsequently opened to make it absolutely safe to work on the circuit breaker which is isolated.
In Document EP A 0 567 773 A2, the disconnector has a fixed pole which is connected to the generator circuit breaker. In order to make it possible to work on the transformer, provision is made to dispose an additional ground disconnector for discharging the transformer after it has been isolated from the generator by opening the circuit breaker and subsequently opening the disconnector, and from the medium voltage or high voltage network by opening a network circuit breaker.